exam 3

1. Isometric vs. Isotonic Contractions

• Isometric contraction: Muscle length stays the same, but tension increases (no movement).
  

  • Example: holding a plank.

• Isotonic contraction: Muscle changes length, causing movement.
  

  • Concentric: Muscle shortens (lifting a weight).

  • Eccentric: Muscle lengthens (lowering a weight).

2. Muscles of the Body (Major Areas)

• Shoulder: Deltoid, rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis)

• Back: Trapezius, latissimus dorsi, rhomboids, erector spinae

• Thigh: Quadriceps (rectus femoris, vastus lateralis/medialis/intermedius), hamstrings (biceps femoris, semitendinosus, semimembranosus)

• Legs: Gastrocnemius, soleus, tibialis anterior

• Chest: Pectoralis major/minor

• Abdomen: Rectus abdominis, external oblique, internal oblique, transversus abdominis

• Arms: Biceps brachii, triceps brachii, brachialis, brachioradialis

3. Deepest Abdominal Muscle

• Transversus abdominis – deepest layer, compresses the abdomen.

4. Muscles Used in Mastication (Chewing)

• Masseter

• Temporalis

• Medial pterygoid

• Lateral pterygoid

5. Prime Movers (Agonists) for Major Movements

• Shoulder (Flexion/Extension): Deltoid, latissimus dorsi

• Back (Extension): Erector spinae

• Thigh (Flexion): Iliopsoas
  (Extension): Gluteus maximus

• Leg (Extension): Quadriceps
  (Flexion): Hamstrings

• Chest (Flexion): Pectoralis major

• Abdomen (Flexion): Rectus abdominis

• Arm (Flexion): Biceps brachii
  (Extension): Triceps brachii

6. Agonist vs. Antagonist vs. Synergist vs. Fixator

• Agonist (Prime Mover): Main muscle causing movement.

• Antagonist: Opposes the agonist.

• Synergist: Assists the agonist.

• Fixator: Stabilizes the origin of the agonist.

Example:

• Biceps brachii (agonist) flexes elbow.

• Triceps brachii (antagonist) extends elbow.

• Brachialis (synergist) helps the biceps.

• Rotator cuff (fixators) stabilize the shoulder.

7. Muscles Have Multiple Roles

• A muscle can be an agonist in one movement, but a synergist or antagonist in another depending on what action is being performed.

8. Muscle Attachment Points

• Origin: Fixed, less movable attachment point (usually proximal).

• Insertion: Movable attachment point (usually distal).

Example:

• Biceps brachii origin: scapula

• Insertion: radius (moves the forearm)

  Chapter 9: Muscles and Muscle Tissue

  1. Sliding Filament Model

  • Explains how muscles contract.

  • Key components:

  • Actin (thin filament)

  • Myosin (thick filament)

  • Tropomyosin (blocks binding sites)

  • Troponin (binds Ca²⁺)

  • Sarcomere shortens as myosin pulls actin inward.

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  2. Appearance of Muscle Fiber

  • Striations are due to repeating sarcomeres.

  • A band: dark (thick filaments)

  • I band: light (thin only)

  • Z line: boundary of sarcomere

  • H zone: center of A band, no actin

  • M line: middle of sarcomere

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  3. ATP Sources for Muscle Fibers

  • Direct phosphorylation (creatine phosphate)

  • Anaerobic glycolysis (2 ATP per glucose)

  • Aerobic respiration – ~32 ATP per glucose

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  4. Muscle Fatigue

  • Inability to contract despite stimulation.

  • Causes:

  • Ion imbalances (K⁺, Ca²⁺)

  • Lack of ATP

  • Accumulation of lactic acid

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  5. 4 Processes Leading to Muscle Contraction

  1. NMJ Activation – Nerve releases ACh

  2. Muscle Fiber Excitation – ACh triggers depolarization

  3. Excitation-Contraction (E-C) Coupling – Action potential releases Ca²⁺

  4. Cross Bridge Cycling – Myosin binds actin, contracts

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  6. Neuromuscular Junction (NMJ)

  • Motor neuron + muscle fiber connection

  • ACh crosses synaptic cleft to activate muscle

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  7. Muscle Cell Types

  • Skeletal – voluntary, striated, multi-nucleated

  • Cardiac – involuntary, striated, gap junctions at intercalated discs

  • Smooth – involuntary, non-striated

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  8. 4 Functions of the Muscular System

  1. Movement

  2. Posture maintenance

  3. Joint stabilization

  4. Heat generation

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  9. Graded Muscle Responses

  • Twitch summation – repeated stimuli before relaxation

  • Recruitment – activating more motor units

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  10. Skeletal Muscle Anatomy

  • Connective tissue layers:

  • Epimysium > Perimysium > Endomysium

  • Organelles:

  • Sarcoplasm, sarcoplasmic reticulum, T-tubules

  • Sarcomere proteins:

  • Actin, myosin, tropomyosin, troponin, titin

  ⸻

  Chapter 8: Joints

  1. 2 Ways to Classify Joints

  • Structural: Fibrous, Cartilaginous, Synovial

  • Functional: Synarthroses (immovable), Amphiarthroses (slightly), Diarthroses (freely movable)

  2. Synovial Joints: 6 General Features

  1. Articular cartilage

  2. Joint cavity

  3. Articular capsule

  4. Synovial fluid

  5. Reinforcing ligaments

  6. Nerves and blood vessels

  3. 5 Main Synovial Joints

  1. Shoulder (glenohumeral) – most mobile

  2. Elbow – hinge, stable

  3. Hip – ball and socket, stable but mobile

  4. Knee – hinge, largest

  5. Temporomandibular joint (TMJ) – modified hinge

  4. 6 Types of Synovial Joints

  Joint Type	Movement	Example
  Plane	Gliding	Intercarpals
  Hinge	Flex/Extend	Elbow
  Pivot	Rotation	Radioulnar joint
  Condylar	Flex/Extend, Ab/Adduct	Wrist
  Saddle	All but rotation	Thumb
  Ball-and-socket	All + rotation	Shoulder/Hip

5. 3 Factors Affecting Joint Stability

1. Articular surface shape

2. Ligament strength/number

3. Muscle tone (most important)

6. 3 General Types of Movement

1. Gliding

2. Angular (flexion, extension, etc.)

3. Rotation

7. Angular Movements

• Flexion: decrease angle

• Extension: increase angle

• Hyperextension: past anatomical position

• Abduction: away from midline

• Adduction: toward midline

• Circumduction: circular motion

Rotation

• Movement around an axis (e.g., head side to side)

8. Unhappy Triad Injury

• Damages:
  

  • ACL (anterior cruciate ligament)

  • MCL (medial collateral ligament)

  • Medial meniscus

• Caused by lateral blow to the knee when foot is planted.